If $a + b = 3$ and $x + y + z = -10$, what is $3z + 3y + 7b + 3x + 7a$ ?
Answer: $= 7a + 7b + 3x + 3y + 3z$ $= (7) \cdot (a + b) + (3) \cdot (x + y + z)$ $= (7) \cdot (3) + (3) \cdot (-10)$ $= 21 - 30$ $= -9$